The Perian team has announced the release of Perian 1.2, an updated version of their QuickTime component that adds native support for many popular video formats. This version of Perian includes a couple improvements for Snow Leopard and numerous bug fixes. Here is a full list of them from the release notes:

Matroska cover art is now imported as iTunes cover art Video tracks now have their colorspace set based on the size of the video QuickTime Player 10 refused to open some files due to missing type identifiers Worked around 96khz HE-AAC audio tracks not playing or playing noise Extended Front Row subtitle hack to cover 10.6 and reduced its ugliness Worked around re-encoding files with subtitles not working Worked around some MKV embedded fonts being incompatible with 10.6 Fixed RGB HuffYUV video displaying black bars over the video on 10.6 Now compiles under Xcode 3.2 Using a debugger on a process with Perian loaded printed warnings about missing files Fixed decoding of WMA audio tracks Fixed a crash in LoadExternalSubtitlesFromFileDataRef Fixed some VobSub video tracks displaying with wrong colors Better support for tracks with delayed start times Fixed MPEG1/2 in Matroska playing out of order Fixed a crash opening files while they were being downloaded Fixed some top-aligned subtitles being too low Vertical text is re-enabled and works somewhat better